Long-term effects of tillage and nitrogen fertilization on soil C and N fractions in a corn–soybean rotation

Tillage and nitrogen (N) fertilization can influence soil organic matter (SOM) dynamics, but their interactive effects remain contradictory. A long-term (25 yr) corn (Zea mays L.)-soybean (Glycine max L. Merr.) rotation was used to investigate the effect of tillage [moldboard plow (MP) no-till (NT)] N rates (0, 80, 160 kg N·ha −1 ) on carbon (SOC), total (STN), respiration, SOM fractions [particulate (POMC, POMN), mineral-associated (MAOMC, MAOMN), microbial biomass (MBC, MBN)]. Results indicate that NT had 27% higher SOC 24% STN than MP in 0–20 cm depth. Furthermore, stocks (0–20 cm) were 22% 20% higher, respectively, under MP. There significant stratification NT, with a rather uniform distribution The respiration 28%–275% 20%–83% at 0–5 5–10 depths, Interestingly, fertilizer rate or its interaction no impact, except for (tillage × depth). Hence, while addition required adequate grain production increased cumulative plant C inputs, our findings vertical SOC, STN, affected by tillage, thereby influencing resource accessibility subsequent dynamics fractions. Taken together, results support adoption judicious use fertilizers enhancing topsoil storage fertility humid temperate conditions.